Windows XP restricts themes to those digitally signed by Microsoft. To use a custom red theme, you need to patch the uxtheme.dll file.
To enable third-party visual styles, you need to modify your core system files so they accept "unsigned" themes: Install the Watercolor Theme on Windows XP (Tutorial) 26-Feb-2018 — windows xp red theme patched
Not the official "Olive Green" or "Silver." No. The forbidden one. The one whispered about on deep-fryer pixel forums: . Windows XP restricts themes to those digitally signed